CD4+ T cells from elite suppressors are more susceptible to HIV-1 but produce fewer virions than cells from chronic progressors.

Elite suppressors/controllers (ES) are HIV-1-infected individuals who maintain stable CD4(+) T-cell counts and viral loads of <50 copies/mL without antiretroviral therapy. Research has predominantly focused on immune factors contributing to the control of viral replication in these patients. A more fundamental question, however, is whether there are differences in the nature of CD4(+) T-cell infection in ES compared with viremic patients. Here, we compare chronic progressor (CP), ES, and uninfected donors in terms of three aspects of CD4(+) T-cell infection: cellular susceptibility to infection, death of infected cells, and production of virus from infected cells. Using multiple methods of infection and both single-cycle and replication-competent virus, we show that unmanipulated CD4(+) T-cell populations from ES are actually more susceptible to HIV-1 infection than those populations from CP. Depletion of highly susceptible cells in CP may contribute to this difference. Using 7AAD and AnnexinV staining, we show that infected cells die more rapidly than uninfected cells, but the increased death of infected cells from CP and ES is proportional. Finally, using an assay for measuring virus production, we show that virus production by cells from CP is high compared with virus production by cells from ES or uninfected donors. This higher virus production is linked to cellular activation levels. These data identify fundamental differences in chronic infection of ES and CP that likely contribute to differential HIV-1 disease progression.

Circulating monocytes are not a major reservoir of HIV-1 in elite suppressors.

Circulating HIV-1-infected monocytes have been identified in patients on highly active antiretroviral therapy and may represent an important barrier to viral eradication. The nature of these cells in HIV-1-infected patients who maintain undetectable viral loads and preserved CD4(+) T cell counts without antiretroviral therapy (known as elite controllers or elite suppressors [ES]) is unknown. We describe here infrequent recovery of proviral HIV-1 DNA from circulating monocytes relative to CD4(+) T cells in ES, despite permissiveness of these cells to HIV-1 viral entry ex vivo. Thus, monocytes do not appear to be a major reservoir of HIV-1 in ES.

Unstimulated primary CD4+ T cells from HIV-1-positive elite suppressors are fully susceptible to HIV-1 entry and productive infection.

Elite controllers or suppressors (ES) are a group of HIV-1-infected individuals who maintain viral loads below the limit of detection of commercial assays for many years. The mechanisms responsible for this remarkable control are under intense study, with the hope of developing therapeutic vaccines effective against HIV-1. In this study, we addressed the question of the intrinsic susceptibility of ES CD4(+) T cells to infection. While we and others have previously shown that CD4(+) T cells from ES can be infected by HIV-1 isolates in vitro, these studies were confounded by exogenous activation and in vitro culture of CD4(+) T cells prior to infection. In order to avoid the changes in chemokine receptor expression that have been associated with such exogenous activation, we infected purified CD4(+) T cells directly after isolation from the peripheral blood of ES, viremic patients, and uninfected donors. We utilized a green fluorescent protein (GFP)-expressing proviral construct pseudotyped with CCR5-tropic or CXCR4-tropic envelope to compare viral entry using a fluorescence resonance energy transfer-based, single-round virus-cell fusion assay. The frequency of productive infection was also compared by assessing GFP expression. CD4(+) T cells from ES were as susceptible as or more susceptible than cells from viremic patients and uninfected donors to HIV-1 entry and productive infection. The results of this physiological study strongly suggest that differences in HIV-1 entry and infection of CD4(+) T cells alone cannot explain the elite control of viral replication.

Viral suppression of multiple escape mutants by de novo CD8(+) T cell responses in a human immunodeficiency virus-1 infected elite suppressor.

Elite suppressors or controllers (ES) are HIV-1 infected patients who maintain undetectable viral loads without treatment. While HLA-B*57-positive ES are usually infected with virus that is unmutated at CTL epitopes, a single, dominant variant containing CTL escape mutations is typically seen in plasma during chronic infection. We describe an ES who developed seven distinct and rare escape variants at an HLA-B*57-restricted Gag epitope over a five year period. Interestingly, he developed proliferative, de novo CTL responses that suppressed replication of each of these variants. These responses, in combination with low viral fitness of each variant, may contribute to sustained elite control in this ES.

Prolonged control of replication-competent dual- tropic human immunodeficiency virus-1 following cessation of highly active antiretroviral therapy.

BACKGROUND: While initiation of highly active antiretroviral therapy (HAART) during primary HIV-1 infection occasionally results in transient control of viral replication after treatment interruption, the vast majority of patients eventually experience a rebound in plasma viremia. RESULTS: Here we report a case of a patient who was started on HAART during symptomatic primary infection and who has subsequently maintained viral loads of < 50 copies/mL for more than nine years after the cessation of treatment. This patient had a high baseline viral load and has maintained a relatively high frequency of latently infected CD4(+) T cells. In addition, he does not have any known protective HLA alleles. Thus it is unlikely that he was destined to become a natural elite controller or suppressor. The mechanism of control of viral replication is unclear; he is infected with a CCR5/CXCR4 dual-tropic virus that is fully replication-competent in vitro. In addition, his spouse, who transmitted the virus to him, developed AIDS. The patient's CD4(+) T cells are fully susceptible to HIV-1 infection, and he has low titers of neutralizing antibodies to heterologous and autologous HIV-1 isolates. Furthermore, his CD8(+) T cells do not have potent HIV suppressive activity. CONCLUSION: This report suggests that some patients may be capable of controlling pathogenic HIV-1 isolates for extended periods of time after the cessation of HAART through a mechanism that is distinct from the potent cytotoxic T lymphocyte (CTL) mediated suppression that has been reported in many elite suppressors.

Control of HIV-1 in elite suppressors despite ongoing replication and evolution in plasma virus.

A subset of HIV-1-infected patients known as elite controllers or suppressors (ES) control the virus naturally. We have previously demonstrated sequence discordance between proviral and plasma gag clones in ES, much of which can be attributed to selective pressure from the host (J. R. Bailey, T. M. Williams, R. F. Siliciano, and J. N. Blankson, J. Exp. Med. 203:1357-1369, 2006). However, it is not clear whether ongoing viral replication continues in ES once the control of viremia has been established or whether selective pressure impacts this evolution. The cytotoxic T-lymphocyte (CTL) response in ES often targets Gag and frequently is superior to that of HIV-1 progressors, partially due to the HLA class I alleles B*57/5801 and B*27, which are overrepresented in ES. We therefore examined longitudinal plasma and proviral gag sequences from HLA-B*57/5801 and -B*27 ES. Despite the highly conserved nature of gag, we observed clear evidence of evolution in the plasma virus, largely due to synonymous substitutions. In contrast, evolution was rare in proviral clones, suggesting that ongoing replication in ES does not permit the significant reseeding of the latent reservoir. Interestingly, there was little continual evolution in CTL epitopes, and we detected de novo CTL responses to autologous viral mutants. Thus, some ES control viremia despite ongoing replication and evolution.

A case of seronegative HIV-1 infection.

Patients infected with human immunodeficiency virus type 1 (HIV-1) typically seroconvert within weeks of primary infection. In rare cases, patients do not develop antibodies against HIV-1 despite demonstrable infection. We describe here a human leukocyte antigen (HLA)-B*5802-positive individual who presented with acquired immune deficiency syndrome despite repeatedly negative HIV-1 antibody screening test results. Phylogenetic analysis of env clones revealed little sequence diversity, and weak HIV-1-specific CD8(+) T cell responses were present to Gag epitopes. The patient seroconverted after immune reconstitution during receipt of highly active antiretroviral therapy. Lack of an antibody response to HIV-1 is rare and appears to be due to a defect in HIV-1-specific immunity rather than infection with attenuated virus.

Evolution of the HIV-1 nef gene in HLA-B*57 positive elite suppressors.

Elite controllers or suppressors (ES) are HIV-1 infected patients who maintain viral loads of < 50 copies/ml without antiretroviral therapy. CD8+ T cells are thought to play a key role in the control of viral replication and exert selective pressure on gag and nef in HLA-B*57 positive ES. We previously showed evolution in the gag gene of ES which surprisingly was mostly due to synonymous mutations rather than non-synonymous mutation in targeted CTL epitopes. This finding could be the result of structural constraints on Gag, and we therefore examined the less conserved nef gene. We found slow evolution of nef in plasma virus in some ES. This evolution is mostly due to synonymous mutations and occurs at a rate similar to that seen in the gag gene in the same patients. The results provide further evidence of ongoing viral replication in ES and suggest that the nef and gag genes in these patients respond similarly to selective pressure from the host.

Role of natural killer cells in a cohort of elite suppressors: low frequency of the protective KIR3DS1 allele and limited inhibition of human immunodeficiency virus type 1 replication in vitro.

Natural killer (NK) cells are associated with the innate immune response and are important in many viral infections. Recent studies indicate that NK cells can control human immunodeficiency virus type 1 (HIV-1) replication. We studied the effect of NK cells on HIV-1 replication in a subpopulation of HIV-1-infected individuals termed elite suppressors (ES) or elite controllers. These patients maintain a clinically undetectable viral load without treatment and thus provide a fascinating cohort in which to study the immunological response to HIV-1. Using an autologous system, we analyzed the effects of NK cells and CD8(+) T cells on viral replication in CD4(+) T lymphoblasts. Although we had postulated that NK cells of ES would be highly effective at controlling viral replication, we found that NK cells from some, but not all, ES were capable of inhibiting replication in the presence of interleukin-2, and the inhibition was less robust than that mediated by CD8(+) T cells. Additionally, we examined whether particular alleles of the KIR receptors, specifically KIR3DS1 and KIR3DL1, or allele-ligand combinations correlated with the control of HIV-1 replication by NK cells and whether any specific KIR alleles were overrepresented in ES. Our ES cohort did not differ from the general population with respect to the frequency of individual KIR. However, of the eight ES studied, the four exhibiting the most NK cell-mediated control of viral replication also had the fewest activating KIR and were haplotype A. Thus, the strong NK cell-mediated inhibition of viral replication is not necessary for the immunological control of HIV-1 in all ES.

Evidence of CD8+ T-cell-mediated selective pressure on human immunodeficiency virus type 1 nef in HLA-B*57+ elite suppressors.

Elite suppressors (ES) are human immunodeficiency virus type 1 (HIV-1)-infected patients who maintain viral loads of <50 copies/ml without treatment. The observation that the HLA-B*57 allele is overrepresented in these patients implies that HIV-1-specific CD8(+) T cells play a key role in suppressing viral replication. We have previously shown that while CD8(+) T-cell escape mutations are rarely seen in proviral Gag sequences in resting CD4(+) T cells from peripheral blood, they are present in every clone amplified from the low levels of free virus in the plasma of HLA-B*57(+) ES. In this study, we compared the pattern of mutations in Nef sequences amplified from peripheral blood CD4(+) T cells and from plasma virus. We show that Nef mutations are present in plasma virus but are rare in the cellular sequences and provide evidence that these plasma Nef variants represent novel escape mutants. The results provide further evidence of CD8(+) T-cell-mediated selective pressure on plasma virus in ES and suggest that there must be ongoing HIV-1 replication in spite of the very low viral loads seen for these patients.

HIV-1 evolution following transmission to an HLA-B*5801-positive patient.

The human immunodeficiency virus type 1 (HIV-1)-specific immune responses of patients with the HLA-B*57/5801 alleles who spontaneously control viral replication serve as an important model for T cell-based HIV-1 vaccines. Determining the breadth of this response and the extent of virologic escape in primary infection in these patients is therefore critical. Here we document the development of mutations in 3 HLA-B*5801-restricted epitopes in gag, nef, and pol in an HLA-B*5801-positive patient who had a viral load of only 1159 copies/mL at day 167 after infection. A full genome sequence analysis was performed to determine the extent of mutations in HLA-B*5801-restricted epitopes, and longitudinal sequence data of specific genes were combined with enzyme-linked immunospot assay analysis of critical epitopes to determine the importance of escape mutations. Thus, relative control of viral replication can be maintained in spite of the rapid development of multiple escape mutations within cytotoxic T lymphocyte epitopes.

T cell dynamics and the response to HAART in a cohort of HIV-1-infected elite suppressors.

Elite controllers or suppressors are untreated human immunodeficiency virus type 1 (HIV-1)-infected patients who maintain undetectable viral loads. In this study, we show that most elite suppressors do not experience significant changes in T cell counts over a 10-year period. Interestingly, treatment of an elite suppressor with highly active antiretroviral therapy (HAART) led to a marked decrease in immune activation.

Host factors dictate control of viral replication in two HIV-1 controller/chronic progressor transmission pairs.

Viremic controllers and elite controllers/suppressors maintain control over HIV-1 replication. Some studies have suggested that control is a result of infection with a defective viral strain, while others suggested host immune factors have a key role. Here we document two HIV-1 transmission pairs: one consisting of a patient with progressive disease and an individual who became an elite suppressor, and the second consisting of a patient with progressive disease and a viremic controller. In contrast to another elite suppressor transmission pair, virus isolated from all patients was fully competent. These data suggest that some viremic controllers and elite suppressors are infected with HIV-1 isolates that replicate vigorously in vitro and are able to cause progressive disease in vivo. These data suggest that host factors have a dominant role in the control of HIV-1 infection, thus it may be possible to control fully pathogenic HIV-1 isolates with therapeutic vaccination.

Sustained elite suppression of replication competent HIV-1 in a patient treated with rituximab based chemotherapy.

The mechanism of elite control of HIV-1 replication is not fully understood. While immunosuppression due to rituximab based chemotherapy has been associated with increased replication of HBV, CMV, and HIV-1, control of replication-competent HIV-1 was maintained in an elite controller/suppressor treated with a regimen that included vincristine, cyclophosphamide, prednisone, four rounds of plasmapheresis and ten cycles of rituximab. The data suggests that de-novo antibody responses do not play a significant role in the control of viral replication in these patients.

Prolonged control of an HIV type 1 escape variant following treatment interruption in an HLA-B*27-positive patient.

The HLA-B*27 allele is overrepresented in patients who control HIV-1 replication without antiretroviral therapy. CD8(+) T cell responses that target the immunodominant KK10 epitope in Gag are thought to play a major role in this control, and escape at R264 of KK10 is often associated with dramatic virologic breakthrough. We present a case in which an HLA-B*27-positive chronic progressor transmitted HIV-1 to an HLA-B*27-positive viremic controller who was temporarily on HAART, but who has since controlled viremia for over 4 years. We hypothesized that differences in the KK10 epitope of these patients would affect pathogenesis and viral fitness, but found no correlation between autologous KK10 mutations and disease progression or between the predicted fitness impact of autologous HLA-B*27-associated mutations and the actual fitness of autologous virus. This case of viral transmission between two HLA-B*27-positive individuals provides further evidence that prolonged control of fully pathogenic HIV-1 is possible.

HIV-1 Gag evolution in recently infected human leukocyte antigen-B*57 patients with low-level viremia.

We studied viral evolution in five human leukocyte antigen (HLA)-B*57 patients recently infected with HIV-1. Escape mutations in HLA-B*57-restricted Gag epitopes were present at study entry in all patients, but were not associated with significant increases in viremia. Conversely, no new escape mutations in HLA-B*57-restricted epitopes or known compensatory mutations were detected in patients who experienced significant increases in viremia. Thus, the development of escape mutations alone does not determine virologic outcome in recently infected HLA-B*57 patients.

Elucidating the elite: mechanisms of control in HIV-1 infection.

In patients with progressive disease, untreated HIV-1 infection is characterized by high viral loads and decreasing CD4(+)T cell counts which lead to opportunistic infection and other AIDS-defining illness. A rare subset of patients termed 'elite controllers' (ECs) maintain control over viremia and often retain normal CD4(+)T cell levels without treatment with antiretroviral drugs. For the most part these patients are infected with replication-competent, fit virus. Factors such as strong, polyfunctional cytotoxic T lymphocyte (CTL) responses and retention of T cell proliferative ability appear to be important in control of HIV-1. Defining what enables ECs to control viral replication will aid in the development of effective vaccine and treatment regimens. This review will discuss differences between ECs and progressors while emphasizing recent findings on the immunological response of ECs to HIV-1.